1. Field of the Invention
The present invention relates to a method and system using a microcomputer for notifying a vehicle driver that the engine lubricating oil should be replaced when the life of lubricating oil has ended.
2. Description of the Prior Art
Conventional methods of determining the replacement timing for engine lubricating oil rely on the fact that when the vehicle has travelled a distance specified by an automotive vehicle's manufacturer or oil supplier, the lubricating oil is recommended to be replaced with new lubricating oil. The change timing of lubricating oil can vary depending on the user's own decision or otherwise the recommendation of a serviceman of a gas station, since there is no definite index for such a replacement determination. The reason that the life of the lubricating oil is usually determined by the total travel distance is that deterioration of the lubricating oil due to aging and thermal load and the amount of soot intermixed or suspended in the lubricating oil, particularly in a diesel engine, is directly related to the total distance of travel.
However, such a conventional method of determining the oil exchange timing is based on a prediction from empirical data, and not on the individual operating conditions. In other words, since the impurities suspended in the lubricating oil depend strictly on the number of engine revolutions, load, EGR rate (Exhaust Gas Recirculation) and so forth, the life calculated solely from the total distance of travel does not always agree with the real life of the oil.
Therefore, there is a problem in that excessively prolonged use of lubricating oil under severe operating conditions shortens engine life and excessively premature replacement of lubricating oil is ineconomical since there is no definite way to determine the optimum change timing for lubricating oil.